In some boiler and burner designs, it may be desirable to transfer at least a portion of combustion energy as radiated energy. However, some types of flames are poorly radiating. In some cases, heat is radiated by flame impinging on a higher-emissivity refractory surface. However, this is not possible in all furnaces. Even when refractory walls can be used, hard refractory walls add weight and cost to furnace installations.
Fuels with a relatively high C/H atomic ratio, e.g., heavy fuel oils and coal, may be used to produce relatively high emissivity flames. However, these fuels are also prone to higher particulate and carbon monoxide (CO) emissions.
Cleaner burning fuels such as natural gas exhibit relatively poor heat transfer via thermal radiation owing to low emissivity of their flames.
What is needed is a technology that can transform a poorly radiating flame into a highly radiating flame. Better radiant heat transfer can reduce the size of a furnace. Furnace size is a significant component of overall reactor or heater cost. Such a technology could reduce the overall size, weight, and cost of new furnaces and increase the throughput of existing furnaces and processes driven by furnaces. Additionally, such a technology would desirably be switchable to allow for rapid heating and cooling cycles not possible with designs having high thermal mass. Moreover, such a technology would desirably offer directed radiation difficult or impossible to achieve with high thermal mass, intermediate radiator approaches.